Causes of blurred vision (reduced visual acuity) include refractive error, corneal opacities, cataract, intraocular inflammation (uveitis), vitreous hemorrhage, retinal detachment involving the macula, diabetic retinopathy, central retinal vein occlusion, central retinal artery occlusion, macular degeneration, and optic nerve disorders.
Monocular field loss is usually due to disease of the retina or optic nerve (eFigure 7–2). Important causes are chronic glaucoma, retinal detachment, branch retinal artery or vein occlusion, optic neuritis, and anterior ischemic optic neuropathy, all of which, especially chronic glaucoma, may be bilateral. Lesions of the optic chiasm, usually due to pituitary tumors, typically cause bitemporal field loss. Retrochiasmal lesions, usually due to cerebrovascular disease or tumor, cause contralateral homonymous hemianopic field loss.
Visual field defects due to various lesions of the optic pathways. (Reproduced, with permission, from Riordan-Eva P, Augsburger JJ. Vaughan & Asbury’s General Ophthalmology, 19th ed. McGraw-Hill, 2018.)
Patients with visual loss not due to refractive error should be referred to an ophthalmologist emergently if it is associated with pain or marked redness or is due to central retinal artery occlusion, retinal detachment with good central vision, or giant cell arteritis. Patients should be referred urgently if the visual loss is associated with redness; due to vitreous hemorrhage, retinal detachment, retinal vein occlusion, branch retinal artery occlusion, diabetic maculopathy, ischemic optic neuropathy, optic neuritis, or thyroid eye disease; or if sudden due to macular degeneration.
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